<communications> Any part of a signal that is not the true or
original signal but is introduced by the communication
mechanism.
A common example would be an electrical signal travelling down
a wire to which noise is added by inductive and capacitive
coupling with other nearby signals (this kind of noise is
known as "crosstalk").
A less obvious form of noise is quantisation noise, such as
the error between the true colour of a point in a scene in the
real world and its representation as a pixel in a digital
image.
